The present invention relates to a microscope provided with an objective lens having a function of correcting an aberration due to an error in the thickness of a cover glass or in the thickness of a member with transmittivity holding a specimen, for example, a Petri dish or a slide glass.
Recently, the main focus in the field of biology has been shifting from the conventional observation of cells to the investigation of mechanisms of information transfer between cells. This trend has highlighted the need for higher performance microscopes and objective lenses.
Generally, an objective lens used in a microscope is designed on the premise that the thickness of a plane-parallel plate such as a cover glass is constant. Accordingly, if the thickness of a cover glass etc. fluctuates greatly, outside the design tolerance, the image forming performance of the objective lens is deteriorated. This tendency is more pronounced in high-performance objective lenses that have larger numerical apertures.
Furthermore, the image forming performance of the objective lens is deteriorated by an error in the thickness of a member with transmittivity holding a specimen such as a Petri dish or a slide glass often used in the observation under an inverted microscope.
To guard against it, a so-called correcting ring-fitted objective lens has been made available which corrects the aberrations by changing a distance between a plurality of lenses mounted in an objective lens corresponding to a change in the thickness of a cover glass or in the thickness of a member with transmittivity such as a Petri dish and slide glass, as disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 5-119263 and 8-114747.
The above-mentioned publications employ a method of correcting aberrations due to an error in the thickness of a cover glass by moving along an optical axis a group of aberration correcting lenses in an objective lens.
To correct an aberration of the cover glass thickness in observation using a microscope, after a specimen comes into focus, the correcting ring of the objective lens is turned so as to improve the resolution. When the aberration is thus corrected, however, the specimen goes out of focus and so must be focused again, thus leading to the problem of much labor being required.
It is an object of the present invention to provide a microscope which can hold a specimen in focus even when an objective lens thereof is corrected in terms of aberration.
To achieve this object, the microscope according to the present invention comprises:
an aberration correcting objective lens facing a specimen and having a movable aberration correcting lens correcting an aberration due to an error in the thickness of a cover glass covering the specimen and a specimen-holding member with transmittivity holding the specimen;
a moving amount detector detecting a moving amount by which the aberration correcting lens moves along an optical axis of the aberration correcting lens;
focusing unit changing a distance between the specimen and the aberration correcting objective lens;
a driver unit driving the focusing unit; and
an arithmetic unit obtaining a defocus amount of the aberration correcting objective lens based on a moving amount detected by the moving amount detector. In such a configuration, when the aberration correcting lens has moved, the specimen is put out of focus of the aberration correcting objective lens. Then, the driver unit drives the focusing unit so as to focus the aberration correcting objective lens, based on a defocus amount obtained by the arithmetic unit.
When correcting an error in the thickness of a cover glass or thickness of a specimen-holding member with transmittivity such as a Petri dish or a slide glass, a defocus amount is obtained which is related to a moving amount of the aberration correcting lens detected by the moving amount detector. The focusing unit changes the distance between the specimen and the aberration correcting objective lens by this defocus amount. This enables proper focusing even when the aberration correcting lens is moved to correct an aberration.
Furthermore, the microscope according to the present invention comprises:
an aberration correcting objective lens facing a specimen and having a movable aberration correcting lens correcting an aberration due to an error in the thickness of a cover glass covering the specimen or a specimen-holding member with transmittivity holding the specimen;
a moving unit moving the aberration correcting lens along an optical axis of the aberration correcting lens;
a focusing unit changing a distance between the specimen and the aberration correcting objective lens;
a driver unit driving the focusing unit; and
an arithmetic unit obtaining a defocus amount of the aberration correcting objective lens based on a moving amount by which the aberration correcting lens is moved by the moving unit. In this configuration, when the aberration correcting lens is moved, the specimen is put out of focus of the aberration correcting objective lens. The driver unit then drives the focusing unit so as to properly focus the aberration correcting objective lens, based on a defocus amount obtained by the arithmetic unit.
When correcting an error in the thickness of a cover glass or the thickness of a specimen-holding member with transmittivity such as a Petri dish or a slide glass, a defocus amount is obtained which is related to a moving amount by which the aberration correcting lens is moved by the moving unit. The focusing unit changes the distance between the specimen and the aberration correcting objective lens by this defocus amount. This enables proper focusing even when the aberration correcting lens is moved to correct an aberration.
Furthermore, the microscope according to the present invention comprises:
a state placing thereon a specimen which is covered by a cover glass or held in a specimen-holding member with transmittivity;
an aberration correcting objective lens facing the above-mentioned stage and having an aberration correcting unit correcting an aberration due to an error in the thickness of the above-mentioned cover glass or specimen-holding member;
a focusing unit changing a distance between the above-mentioned stage and the above-mentioned aberration-collecting objective lens;
an optical observation system leading the light from the above-mentioned specimen that has passed through the above-mentioned aberration correcting objective lens, to form an observed image of the specimen; and
a processor section controlling the above-mentioned focusing unit so as to focus the above-mentioned aberration correcting objective lens. In this configuration, when the above-mentioned aberration correcting unit has corrected an aberration, the specimen is put out of focus of the above-mentioned aberration correcting objective lens. Then, the above-mentioned processor section controls the above-mentioned focusing unit so that the above-mentioned aberration correcting objective lens may focus on the specimen.
Defocusing occurs if the aberration correcting lens is moved to correct an error in the thickness of the cover glass or the thickness of the specimen-holding member with transmittivity such as a Petri dish or a slide glass. The microscope according to the present invention is provided with the processor section controlling the focusing unit so that the specimen may be put in focus, thus modifying a defocus due to the movement of the aberration correcting lens. By utilizing those abilities of modification of a defocus and movement of the aberration correcting lens, it is possible to find an optimal focal point and also to realize an observation state in which such an aberration has been corrected that is caused by an error in the cover glass thickness.
In the microscope according to the present invention, the above-mentioned aberration correcting objective lens has an objective lens body. The above-mentioned aberration correcting unit has an aberration correcting lens movably attached to the objective lens body. The microscope according to the present invention further comprises:
a moving unit moving the above-mentioned aberration correcting lens;
a photo-detector with a light-receiving plane detecting a light incident upon this light-receiving plane; and
an optical detector system leading onto the above-mentioned light-receiving plane of the above-mentioned photo-detector the light from the above-mentioned specimen that has passed trough the above-mentioned aberration correcting objective lens. In this configuration, the above-mentioned processor section obtains a contrast of an image of the above-mentioned specimen formed on the above-mentioned light-receiving plane from the light detected by the above-mentioned photo-detector and, based on this contrast, controls the above-mentioned moving unit and focusing unit. As a result, the above-mentioned aberration correcting objective lens is well focused on the specimen, thereby correcting an aberration of the observed image.
A defocus due to the movement of the aberration correcting lens can be modified by changing the distance between the stage and the objective lens by as much as a predetermined amount (defocus amount). In the microscope according to the present invention, the above-mentioned processor section obtains a contrast of an image of the specimen formed on the light-receiving plane. Based on this contrast, the processor section calculates, for example, a defocus amount. Based on this defocus amount, the processor section controls the moving unit and the focusing unit. As a result, an optimal focus position can be found and also an observation state can be realized in which an aberration due to an error in the cover glass thickness has been corrected.
The microscope according to the present invention further comprises:
at least one regular objective lens; and
an objective-lens selector mechanism selectively setting a first state in which the above-mentioned aberration correcting objective lens faces the above-mentioned stage and the regular objective lens is placed far away from the above-mentioned stage and a second state in which the above-mentioned aberration correcting objective lens is placed far away from the above-mentioned stage and one of the regular objective lenses faces the above-mentioned stage.
When the regular objective lens is facing the stage, the lens is focused with the aberration of an observed image as uncorrected. If the aberration correcting objective lens is facing the stage, on the other hand, the lens is focused with the aberration of the observed image as corrected.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.